It sounded to me like the guy's laughter was more like, "Holy crap! I can't believe I'm seeing this!" than, "HA HA HA! Got ya, Sucka!" He specified that he only killed it to protect his child and his dog and if you watched the entire video, he also said, "Sorry snake," and wasn't laughing when he said it. Is it so far fetched to even entertain the thought that this guy isn't a complete jerk and he just freaked in the moment? Is it completely impossible that he doesn't fancy himself a serpent slayer and wasn't super stoked that he got to cut a snake's head off, that's just what he felt he had to do at the time?
If we believe his commentary, that he killed the snake to protect his child, then he didn't do anything wrong in my opinion. I'd kill anything to protect my child and I wouldn't apologize for it. Let's not be so judgmental. Maybe the guy made a poor choice in posting the video, big deal. I've certainly said and done things that were in poor taste, that doesn't make me a giant piece of crap of a person.